全文获取类型
收费全文 | 2681篇 |
免费 | 135篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 652篇 |
金属工艺 | 46篇 |
机械仪表 | 63篇 |
建筑科学 | 81篇 |
矿业工程 | 3篇 |
能源动力 | 105篇 |
轻工业 | 185篇 |
水利工程 | 12篇 |
石油天然气 | 4篇 |
无线电 | 305篇 |
一般工业技术 | 513篇 |
冶金工业 | 198篇 |
原子能技术 | 11篇 |
自动化技术 | 613篇 |
出版年
2024年 | 2篇 |
2023年 | 30篇 |
2022年 | 43篇 |
2021年 | 67篇 |
2020年 | 63篇 |
2019年 | 55篇 |
2018年 | 75篇 |
2017年 | 63篇 |
2016年 | 93篇 |
2015年 | 66篇 |
2014年 | 106篇 |
2013年 | 186篇 |
2012年 | 200篇 |
2011年 | 241篇 |
2010年 | 181篇 |
2009年 | 155篇 |
2008年 | 153篇 |
2007年 | 159篇 |
2006年 | 105篇 |
2005年 | 94篇 |
2004年 | 73篇 |
2003年 | 52篇 |
2002年 | 55篇 |
2001年 | 59篇 |
2000年 | 35篇 |
1999年 | 46篇 |
1998年 | 80篇 |
1997年 | 45篇 |
1996年 | 34篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 4篇 |
排序方式: 共有2817条查询结果,搜索用时 0 毫秒
181.
In situ Angle Resolved X-ray Photoemission Spectroscopy (ARXPS) characterizations of TiO2 thin films grown on silicon by Metal Organic Chemical Vapour Deposition were performed in order to get information on interfacial reactions at the first stages of the growth, one of the aims being to understand the influence of deposition conditions. Thickness measurements were also carried out from ARXPS analyses. As the real structure of the films was shown to be a double layer system such as TiO2/SiO2/Si, an ARXPS model of thickness and surface coverage determination was applied to each layer independently. However, the application of this model to very thin films underestimates the surface coverage of the interfacial layer. A “Double Layer” model taking into account the attenuation of the silicon oxide and substrate signals by the external layer was also developed. 相似文献
182.
Moncef Hidane Olivier Lézoray Abderrahim Elmoataz 《Journal of Mathematical Imaging and Vision》2013,45(2):114-137
We propose a nonlinear multiscale decomposition of signals defined on the vertex set of a general weighted graph. This decomposition is inspired by the hierarchical multiscale (BV,L 2) decomposition of Tadmor, Nezzar, and Vese (Multiscale Model. Simul. 2(4):554–579, 2004). We find the decomposition by iterative regularization using a graph variant of the classical total variation regularization (Rudin et al, Physica D 60(1–4):259–268, 1992). Using tools from convex analysis, and in particular Moreau’s identity, we carry out the mathematical study of the proposed method, proving the convergence of the representation and providing an energy decomposition result. The choice of the sequence of scales is also addressed. Our study shows that the initial scale can be related to a discrete version of Meyer’s norm (Meyer, Oscillating Patterns in Image Processing and Nonlinear Evolution Equations, 2001) which we introduce in the present paper. We propose to use the recent primal-dual algorithm of Chambolle and Pock (J. Math. Imaging Vis. 40:120–145, 2011) in order to compute both the minimizer of the graph total variation and the corresponding dual norm. By applying the graph model to digital images, we investigate the use of nonlocal methods to the multiscale decomposition task. Since the only assumption needed to apply our method is that the input data is living on a graph, we are also able to tackle the task of adaptive multiscale decomposition of irregularly sampled data sets within the same framework. We provide in particular examples of 3-D irregular meshes and point clouds decompositions. 相似文献
183.
This study compares hot pressing (HP) and the electric field-assisted sintering technique (FAST) of two different electrically insulating Al2O3 submicron powders with median particle sizes of 150 and 500 nm. Sample geometry, heating schedule, applied pressure and atmosphere were identical for both sintering methods. The densification behavior and characterization of the microstructure revealed that FAST sintered samples reached a higher density compared with HP, in particular for the finer powder. It was found that an increase in dwell time was required to reach the same final density by HP. However, analysis of the sintering curves showed that the densification mechanism for both sintering methods was grain boundary diffusion. Increasing the heating rate up to 150 K min?1 did not modify the densification mechanism. The sintering trajectory showed that the grain size was only dependent on density and was insensitive to the sintering method, in addition to showing a lack of preferential grain orientation. 相似文献
184.
Ravichandra S. Jupudi Guillermo Zappi Richard Bourgeois 《Journal of Applied Electrochemistry》2007,37(8):921-931
A model for predicting shunt/leakage currents in a bipolar electrolyzer stack with dual electrolyte inlets and significant
amount of gases in the outlet ports and manifold is presented. Model includes electrolyte, manifold and membrane separator
as resistance components in the electric circuit analog of the stack. Activation overvoltage associated with electrodes is
taken as Tafel-like. Current balance and potential balance equations are applied to the stack and difference calculus is employed
to reduce the problem to a set of linear difference equations with constant coefficients. The model is validated with published
results and the effect of each resistance component and number of cells on leakage currents in the stack is presented.
The U.S. Goverment’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged. 相似文献
185.
Jean-Baptiste Ollagnier Olivier Guillon Jürgen Rödel 《Journal of the American Ceramic Society》2007,90(12):3846-3851
The sintering behavior of a glass–ceramic (commercial material Ceramtape GC) was characterized using the discontinuous sinter-forging technique. The uniaxial viscosity E p and the viscous Poisson's ratio np of the composite body were determined as a function of density. Particular attention was paid to microstructural changes in order to quantify the anisotropy induced by load application. Pores and alumina particles were found to be both oriented perpendicular to the applied load direction. Finally, the experimental results were used to predict the value of the hydrostatic sintering stress. 相似文献
186.
The MPEG- 2 Advanced Audio Coder is the latest issue of the MPEG audio encoders/decoders family, whose most popular version is known as MP3. It gathers many of the latest highly efficient sound compression techniques in a quite classically structured coder. The main part is based on a Discrete Cosine Transform with variable resolution. The output from this filterbank is compressed by the combination of an adaptive bit allocation module, according to frequency subbands, and a set of noiseless Huffman codebooks. Bit allocation is controlled by a psychoa-coustic model which determines an audibility threshold for signal distortion in the frequency domain. This article intends to explain the ISO standard without replacing it, and also to be a general introduction to perceptual audio coding. 相似文献
187.
Field trials in Paris at 855 MHz were used to show that fast fading could be characterised with a 1 m sampling step: the normalised field strength is first shown to be highly uncorrelated between two data points and then its statistical distribution is found to be well fitted by a Rayleigh law. 相似文献
188.
We describe the design of a microwave oscillator using resonant tunneling diodes. The devices are fabricated from Al0.3Ga0.7As-GaAs double barrier hetero-structures grown by molecular beam epitaxy. Design criteria improving current drivability are established from a theoretical study of tunneling transmission probabilities. Very high peak current densities up to 3.104 A/cm2, favorable for high frequency operation as an oscillator, have been achieved experimentally. The devices exhibit stable oscillations at liquid nitrogen temperature and at room temperature when the tunnel diode oscillator is constructed with a stabilizing network. 相似文献
189.
In dry coating processes no liquid, solvent, binder or water, is required. This makes them advantageous compared to wet coating alternative: being low cost, no drying step required, environmentally friendly (no volatile organic compounds related problems) and simple in operation. But there is still a lack of fundamental knowledge of the implied mechanisms. Often the process itself has been empirically designed and is not always well characterized.In this work, some hydrodynamic elements are developed in a high energy mixer used for dry coating: the specific behavior of the Nara hybridizer NHS-0 is investigated. In the first part, recirculation velocities and temperatures are derived during the process, or when the purge is on. The effects of the pressure purge and of the rotor velocity on the purge and the effect of the rotation on the temperature increase are studied. In the second part, a simple experimental approach is carried out to derive qualitatively the local temperature inside the apparatus with the help of polymers with different melting temperatures. This approach illustrates a first step for dry coating application with waxes. 相似文献
190.